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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
OPENWEBGLOBE - AN OPEN SOURCE SDK FOR CREATING
LARGE-SCALE VIRTUAL GLOBES ON A WEBGL BASIS
B. Loesch, M. Christen, S. Nebiker
Institute of Geomatics Engineering, FHNW University of Applied Sciences and Arts Northwestern Switzerland
3
Muttenz, Switzerland — (benjamin.loesch, martin.christen, stephan.nebiker)@fhnw.ch
Commission IV, WG IV/4
KEY WORDS: Visualization, Algorithms, Virtual Reality, Web based, Point Cloud, Three-dimensional, Triangulation
ABSTRACT:
This paper introduces the OpenWebGlobe project (www.openwebglobe.org) and the OpenWebGlobe SDK (Software Development
Kit) — an open source virtual globe environment using WebGL.
toolkits, the OpenWebGlobe SDK not only supports the conte
Unlike other (web-based) 3d geovisualisation technologies and
nt authoring and web visualization aspects, but also the data
processing functionality for generating multi-terabyte terrain, image, map and 3d point cloud data sets in high-performance and
cloud-based parallel computing environments. The OpenWebGlobe architecture is described and the paper outlines the processing
and the viewer functionality provided by the OpenWebGlobe SDK. It then discusses the generation and updating of a global 3d base
map using OpenStreetMap data and finally presents two show cases employing the technology a) for implementing an interactive
national 3d geoportal incorporating high resolution national geodata sets and b) for implementing a 3d geoinformation service
supporting the real-time incorporation of 3d point cloud data.
1. INTRODUCTION
In recent years virtual globes have become an important tool for
interactively visualizing and investigating geo-referenced
content. Virtual globes are capable of streaming terabytes of
imagery, elevation data and other geospatial contents over the
Internet. Emerging Internet technologies, such as HTMLS and
WebGL, offer new possibilities to develop virtual globes
running in web-browsers without a need for browser extensions
or plugins.
WebGL is a cross-platform, royalty-free web standard for a
low-level 3d graphics API based on OpenGL ES 2.0 (WebGL,
2011). It is exposed through the HTMLS Canvas element as
Document Object Model interface. WebGL is a shader-based
API using the OpenGL Shading Language (GLSL), with
constructs that are semantically similar to those of the
underlying OpenGL ES 2.0 API. In March 2011 version 1.0 of
the WebGL specification was released. Today WebGL runs in
desktop and mobile web-browsers like Mozilla Firefox, Google
Chrome, Safari, and Opera. In the Internet Explorer WebGL
can currently only be used through plugins.
Many different JavaScript 3d engines such as three.js (Three.js,
2012) or SceneJS (SceneJS, 2012) were created to ease the
implementation of different 3d web applications or games using
WebGL. It is no surprise that also in the field of virtual globes
WebGL is a hot topic and used for several virtual globe web
applications. Projects like WebGL Earth (WebGL Earth, 2012)
the ReadyMap SDK (Pelican Mapping, 2012) and our
OpenWebGlobe SDK were initiated to provide a base for the
implementation of new 3d virtual globe applications using
WebGL. Also Google is currently working on a WebGL
version of Google Maps (Google Maps, 2012).
Apart from the discussion about the advantages or
disadvantages of a plugin free virtual globe (VG) browser
application, today's VGs also have a number of shortcomings
such as a lack of extensibility in terms of large , complex user-
generated or third-party geospatial contents (c.g. own high-
resolution DTMs or large to very large customized map or
orthoimage data sets). Other potentially more serious
shortcomings are the lacking extensibility in terms of
functionality and the lacking ease of integration into third party
applications and into operational environments which might not
be compatible with data and IP right policies of large
commercial VG operators. The strive for new applications of
VGs together with the above mentioned limitations of the main
commercial VGs have been the motivation for developing our
own VG technology at the FHNW.
In this paper we discuss the evolution of and research activities
in Internet- and web-based interactive 3d technologies. We then
present the OpenWebGlobe project and architecture. The paper
first focuses on the OpenWebGlobe viewer component, which
is fully based on HTMLS and WebGL, as well as some of its
key features. This is followed by a short discussion of the
OpenWebGlobe processing functionality. In the later sections
of this paper we present two applications which were built
using the OpenWebGlobe SDK. First a pilot national 3d
geoportal of Switzerland using high resolution imagery and
elevation data is described. Second an application in which
OpenWebGlobe is used for visualizing continuously generated
point cloud data for rapid mapping and inspection of unknown
buildings or industry-sites.
2. RELATED WORK
Different mechanisms for an interactive visualization of 3d
contents in the web are available and frequently used. Early
formats and standards such as the Virtual Reality Modeling
Language (VRML) (Bell, 1995) were defined in the mid 90ies
and permitted the authoring and delivery of 3d contents over the
web but required applications or browser plugins. VRML was
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